This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. The following descriptions and examples are not admitted to be prior art by virtue of their inclusion in this section.
The present disclosure relates generally to methods and systems for estimating formation slowness. In particular, the present disclosure relates to methods and systems for estimating formation slowness in presence of anisotropy and/or stress in downstream geophysics workflow utilizing sonic measurements.
The downstream geophysics workflow utilizing sonic measurements includes, for example, rock physics modeling, seismic inversion, well ties, Amplitude-Versus-Offset (AVO) modeling and so on, as disclosed in the documents of International Publication No. WO 2010/11077 A1, U.S. Pat. Application Publication No. 2011/0077920 A1, U.S. Pat. Application Publication No. 2006/0153005 A1 and International Publication No. WO 2005/149237 A1, the contents of which are incorporated herein in its entirety by reference thereto. The data of sonic measurements can be received from an acoustic tool and included directly into their geophysical modeling software packages for a quantitative interpretation. However in a number of cases, anisotropy effects, which are either TI (Transverse Isotropy) in shales or stress in sands, are not included in this modeling software. For example, a TI characterization workflow is developed by Jocker et al. (2013), as described in the document of J. Jocker, E. Wielemaker and S. Sunaga, (2013), “TI Anisotropic Model Building Using Borehole Sonic Logs Acquired in Heterogeneous Formations”, SEG Technical Program Expanded Abstracts, pp. 305-309 (2013). The TI Characterization workflow addresses the shales case, yet there are still challenges within the reservoir (e.g. sands) where the slownesses are responding to stress and anisotropy. The challenge is further complicated in deviated wells where verticalized slownesses are mandatory for getting accurate outcomes from seismic workflows.